A speedometer determinea the speed at which the vehicle is moving. The speedometer has two rotating-barrel shaped magnets, one of which is connected to the sleeved cable and the other is connected to the speedometer needle. These magnets are calibrated to detect the revolution speed and the flexible cable connected to these magnets and the speedometer indicates the speed at which the vehicle is moving. This device was invented by Josip Belusic in 1888. The device was electronic like the modern day speedometer.

The speedometer is used in vehicles such as boats, airplane, automobile, bikes, motorcycles, etc. The speedometer used in different type of vehicle have different names assigned to them. One of the types of speedometer that were used in boats was known as airguide speedometer. The airguide speedometer is connected to a tube with a piston inside. Some airguide speedometers could detect speeds from 0 to 50 mph. In addition to the 1 mph gradations for slower speeds, the airguide also had the advantages of a movable speed reference needle and an adjustment knob for precise calibration. Airguide was the defacto standard in adjustable boat speedometers and these had a front adjustment knob that alloweds the user to calibrate by trial and error during timed runs through the slalom course. There have been differing opinions from the subject experts on the accuracy of the airguide speedometers and most of them lack conclusive support.

The airguide speedometer is no longer produced. However they are still purchased from the market as a collector's item or as vintage articles.